[Daryles]

We have an inline water meter we put on the hose.
From bone dry empty (dewinterizing) it takes about 65 gallons. Freshwater tank, pipes and water heater.
Normally filling the freshwater tank takes about 42 gallons. I usually fill it until water overflows out the vent. With the slides out I can't see the vent at the rear but I can see the water running down the sides dripping on the ground and shut off the valve.
Keeping the water in the tank while driving is another challenge.
If you take a right hand clover leaf exit coming off the highway, the centerfugal force will push the water out the vent overflow. You arrive with less than half a tank.
Put a Rubber boat drain plug in the freshwater vent to prevent this.
Just don't forget to remove it upon arrival or you will collapse your freshwater tank when you use your water and air can't get into the tank.